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POHow to wait until all child processes called by fork() complete?
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  1. POHow to wait until all child processes called by fork() complete?
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    copied!<p>I am forking a number of processes and I want to measure how long it takes to complete the whole task, that is when all processes forked are completed. Please advise how to make the parent process wait until all child processes are terminated? I want to make sure that I stop the timer at the right moment.</p> <p>Here is as a code I use:</p> <pre><code>#include &lt;iostream&gt; #include &lt;string&gt; #include &lt;fstream&gt; #include &lt;sys/time.h&gt; #include &lt;sys/wait.h&gt; using namespace std; struct timeval first, second, lapsed; struct timezone tzp; int main(int argc, char* argv[])// query, file, num. of processes. { int pCount = 5; // process count gettimeofday (&amp;first, &amp;tzp); //start time pid_t* pID = new pid_t[pCount]; for(int indexOfProcess=0; indexOfProcess&lt;pCount; indexOfProcess++) { pID[indexOfProcess]= fork(); if (pID[indexOfProcess] == 0) // child { // code only executed by child process // magic here // The End exit(0); } else if (pID[indexOfProcess] &lt; 0) // failed to fork { cerr &lt;&lt; "Failed to fork" &lt;&lt; endl; exit(1); } else // parent { // if(indexOfProcess==pCount-1) and a loop with waitpid?? gettimeofday (&amp;second, &amp;tzp); //stop time if (first.tv_usec &gt; second.tv_usec) { second.tv_usec += 1000000; second.tv_sec--; } lapsed.tv_usec = second.tv_usec - first.tv_usec; lapsed.tv_sec = second.tv_sec - first.tv_sec; cout &lt;&lt; "Job performed in " &lt;&lt;lapsed.tv_sec &lt;&lt; " sec and " &lt;&lt; lapsed.tv_usec &lt;&lt; " usec"&lt;&lt; endl &lt;&lt; endl; } }//for }//main </code></pre>
 

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